This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Sweden Application No. 0001825-9 filed on May 18, 2000, the entire content of which is incorporated herein by reference.
The present invention relates to a tool coupling, preferably for rotary tools, intended to rotate around an axis of rotation. The tool coupling serves to couple together a drive member and a tool body intended to carry cutting inserts for chip removing machining. The tool coupling comprises a toothed male part and a toothed female part, which parts are intended to be received one in the other.
A coupling element which can be coupled together with another member for the transmission of a rotation movement therebetween, wherein said coupling element may consist of a screw head, for example, is previously known from U.S. Pat. No. 3,584,667.
The coupling element according to U.S. Pat. No. 3,584,667 comprises a first series of spaced-apart, partially cylindrical convex surfaces and a second series of partially cylindrical concave surfaces alternating with the surfaces of the first series and connected tangentially thereto. The radius of curvature of the partially cylindrical concave surfaces included in the second series is considerably larger than the radius of curvature of the partially cylindrical convex surfaces included in the first series. Screws with screw heads formed as coupling elements according to U.S. Pat. No. 3,584,667 are marketed under the trademark TORX(copyright). During the transmission of a rotational movement, a socket wrench having a corresponding, although inverted, design as the screw head is, for instance, used, said socket wrench being mated with the screw head. The so-called TORX(copyright) system enables transfer of high torques between socket wrench and screw head. The TORX(copyright) system also comprises screw heads having countersunk holes featuring the TORX(copyright) configuration.
A replaceable cutting body, i.e., a so-called loose top that is attached to a shaft is previously known from German Document 34 02 547. The connection between the cutting body and the shaft is formed in such a way that three radial grooves are provided in the end of the shaft facing the cutting body, while three radial ridges are arranged on the cutting body. In the active position of the connection, an axial fastenting screw extends through the cutting body and into the shaft, the ridges being received in the grooves. Thereby, a torque may be transferred from the shaft to the cutting body. By virtue of a relatively flat inclination of the co-operating flanks of the grooves and the ridges, a relatively high axial force is required between the shaft and the cutting body in order to transfer torque of the magnitude desired from the shaft to the cutting body. The high axial force may lead to an elongation of the screw. Furthermore, it is difficult to define where abutment between the ridges and grooves will take place since the ridges and grooves have a linear extension.
Aims and Features of the Invention
A primary aim of the present invention is to provide a tool coupling of the kind defined in the introduction. The tool coupling being capable of transmitting large torques.
Another aim of the present invention is that also at a moderate axial pre-tension, there is an exceptionally small risk of failure of the transmission of torque.
Yet another aim of the present invention is that the tool coupling should he self-centering.
An additional aim of the present invention is that the tool coupling is free of play.
At least the primary aim of the present invention is realized by the combination of a driven tool and a drive member. The driven tool defines an axis of rotation and includes a body having at least one seat for receiving a cutting insert. A securing element secures the driven tool to the drive member. The drive member drives the tool about the axis of rotation. The driven tool includes a driven part rotatable about the axis, and the drive member includes a drive part rotatable about the axis and mated with the driven part to form a drive coupling therewith. The drive part and the driven part are conical as viewed in a longitudinal section plane containing the axis, and are arranged one inside of the other. The driven part includes driven teeth projecting generally radially with respect to the axis and received in respective radially-open recesses formed in the drive part. Each of the driven teeth terminates in an axially facing wall and includes a sidewall contacting a sidewall of the recess. A curvature of the tooth sidewall is different from a curvature of the recess sidewall at locations where those sidewalls contact one another. Accordingly, such contact is in the form of a point contact on each side of a generally radial line of symmetry of the respective tooth as viewed in a direction parallel to the axis. Each of the contact points is operable to transmit a drive fore from the drive part to the driven part in a respective direction of rotation. Each of the contact points defines a tangent line, wherein the drive force is transmitted along a line of force oriented perpendicular to a respective tangent line. A driving angle is formed between the line of symmetry and each tangent line. Each driving angle is in the range of xe2x88x925xc2x0 to +45xc2x0.